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Cloud top pressure. What does it mean to climate? The aerosol forcing corresponding to the ... the correlation of aerosol AOT and properties to cloud cover & height ...

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slide1
Aerosol effect on cloud cover and cloud height

Kaufman, Koren, Remer, Rosenfeld & Martins

slide2
Koren, I., Y. J. Kaufman L. A. Remer and J.V. Martins, Measurement of the effect of Amazon smoke on inhibition of cloud formation, Science, 303, 1342-1344, 2004. http://climate.gsfc.nasa.gov/publications/fulltext/Koren_et_al._(2004).pdf
  • Kaufman, Y. J., I. Koren, L. A. Remer, D. Rosenfeld and Y. Rudich, The effect of smoke, dust, and pollution aerosol on shallow cloud development over the Atlantic Ocean, Proc. Nat. Acad. Scie., 102, 11207-11212, 2005http://climate.gsfc.nasa.gov/publications/fulltext/PNAS-shallow_clouds.pdf
  • Koren, I. Y. J. Kaufman, L. A. Remer, D. Rosenfeld and Y. RudichAerosol impact on the development and coverage of Convective clouds, Geoph. Res. Lett. 32 (14): Art. No. L14828 JUL 30 2005 http://climate.gsfc.nasa.gov/publications/fulltext/2005GL023187.pdf
slide5
Koren et al Science, 2004;

Cloud fraction as function of aerosol optical depth (OD). The cloud fraction decreases almost linearly with increasing OD.

slide6
Clouds only

+8w/m2

-28w/m2

Smoke only

Impacts:

• smoke instantaneous forcing -28w/m2 --> +8w/m2

• smoke 24hrs forcing -11w/m2 --> -5w/m2

• less radiation at the surface => less evaporation

• smaller boundary layer cloud fraction

slide7
2. Aerosol effects on cloud cover - shallow clouds

The Atlantic Ocean - several aerosol types interacting with clouds June-Aug 2002

Pollution zone

Dust zone

Smoke zone

Marine aerosol

pollution

dust

smoke

Sea salt

convective

convective

stratiform

slide8
Dust

Stratus and trade cumulus

Clouds

Smoke

slide10
clean

hazy

Cloud fraction

Cloud fraction

clean

hazy

Cloud top pressure

Cloud top pressure

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What does it mean to climate?

The aerosol forcing corresponding to the increase in cloud cover is ~ 6w/m2 in the June-Aug period over the Atlantic Ocean

We see similar increases in other locations, depending on the aerosol content of black carbon.

How does it reconcile with global warming?

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x. What is the response of the cloud water path to 50 yr increase in aerosol concentration?

A. Fixed ocean temperature

B. feedback through ocean temperature

Takemura, Kaufman, Remer, Nakajima, submitted

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Aerosol effect on cloud cover and cloud height

• MODIS is in unique position to measure the correlation of aerosol AOT and properties to cloud cover & height

• We find increases in cloud cover on average of 0.05 → ~ 6 W/m2

• We find an average increase in cloud height of ~ 400 m (-40 mb)

• Model shows that long term aerosol cooling of the ocean may compensate the aerosol effect on cloud cover through impact on cloud microphysics

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